[30/68] tcp: Increase TCP_MAXSEG socket option minimum.

From: Greg KH
Date: Mon Feb 28 2011 - 11:47:36 EST

2.6.32-longterm review patch. If anyone has any objections, please let us know.


From: David S. Miller <davem@xxxxxxxxxxxxx>

commit 7a1abd08d52fdeddb3e9a5a33f2f15cc6a5674d2 upstream.

As noted by Steve Chen, since commit
f5fff5dc8a7a3f395b0525c02ba92c95d42b7390 ("tcp: advertise MSS
requested by user") we can end up with a situation where
tcp_select_initial_window() does a divide by a zero (or
even negative) mss value.

The problem is that sometimes we effectively subtract

Fix this by increasing the minimum from 8 to 64.

Reported-by: Steve Chen <schen@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Moritz Muehlenhoff <jmm@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

net/ipv4/tcp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2117,7 +2117,7 @@ static int do_tcp_setsockopt(struct sock
/* Values greater than interface MTU won't take effect. However
* at the point when this call is done we typically don't yet
* know which interface is going to be used */
- if (val < 8 || val > MAX_TCP_WINDOW) {
+ if (val < 64 || val > MAX_TCP_WINDOW) {
err = -EINVAL;

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